Filter cigarette



M y 1967 R. J. CHAMBERLAIN FILTER CIGARETTE Filed May 20, 1965 1N VENTOR. RALPH J. CHAMBERLAIN A TTORNEY United States Patent Ofiice 3,319,629 Patented May 16, 1967 3,319,629 FILTER CIGARETTE Ralph Joseph Chamberlain, Gienbrook, Conn., asslgnor to American Cyanamid Company, Stamford, Conn., a corporation of Maine Filed May 20, 1965, Ser. No. 457,281 3 Claims. (Cl. 131-10) The present invention relates to filter cigarettes having a novel filter element, processes for the manufacture of said cigarettes, and the filter element itself.

At the present time cigarettes generally contain a filter element adapted to remove noxious components from the smoke which is produced when a cigarette burns.

It has long been recognized that activated carbon is efiective and generally desirable as a filter material in cigarettes, being non-toxic and cheap and having a high adsorptive capacity for the noxious elements of cigarette smoke.

Activated carbon is manufactured both highly particulate and-in coarsely granular state. specific surface area, colloidal activated carbon has highest adsorptive capacity for the noxious components in cigarette smoke, but up to the present time, activated carbon in this form has not been found 'to have the physical properties needed for successful use in cigarettes. Highly particulate carbon 325 mesh, i.e. 44 microns in average diameter) when introduced into a cigarette so as to form a filter zone therein, tends to become a compact mass and to block the passage of smoke from the cigarette, and when dispersed into the tobacco near the exit or tip of the cigarette it tends to be picked up by the stream of smoke, causing unsightly blackening of the smokers lips and mouth.

As a result, activated carbon is customarily used in coarse granular state, being present in the cigarette as a filter zone at the tip and being held in place by a porous plug or disc. The carbon is thus present in nonoptimum form, as its adsorptive capabilities for smoke are not at a maximum when it is in coarse granular state.

The discoveries have now been made that highly particulate activated carbon is strongly self-adsorbed on cationic cyanamide-cellulose acetate tow when such tow is passed through an aqueous suspension of colloidal activated carbon. and that such carbon-containing tow acts as an eflicient filter element in cigarettes. The present invention thus makes colloidal carbon conveniently available as a smoke filtering agent in cigarettes in non-granular state. 'In the filter, the particles of activated carbon are supported in discrete state on filaments of cyanamidecellulose acetate.

The invention is more particularly illustrated by the drawings, wherein:

FIG. 1 is a schematic longitudinal section of a cigarette according to the present invention, and

FIG. 2 is a drawing of a photornicrograph taken at 100x of several filaments of a filter element of the present invention.

In FIG. 1, 1 represents a tube of cigarette paper which contains the tobacco and the filter element of the cigarette; 2 represents an optional tip covering which may be coated paper, plastic, or cork; 3 represents the tobacco whereof the cigarette is principally composed; 4 represents cationic cyanamide-cellulose acetate tow having colloidal activated carbon adsorbed thereon as filter element in said cigarette; and 5 represents an optional porous disc which prevents the tongue of the smoker from wetting the filter element.

In FIG. 2, 6 designates a filament of cyanamide-cellulose acetate tow and 7 designates highly particulate activated carbon thereon.

Because of its high The activated carbon present in the filter element of the present invention is any carbon which has a high adsorptive capacity for organic vapors. Thus the carbon may be charcoal produced by the destructive distillation of vegetable matter (with or without the addition of chemicals), or may be norit, or bone black, or carbon black (lamp black, Paris black) made by partial cornbustion of natural gas.

The activated carbon present in filters of the present invention is highly particulate and in general it is preferred that the particle size of the carbon be as small as possible. The particles may be in the pigmentary range (S to 0.1 but preferably they are in the colloidal range (0.1/1. to 0.00m). This corresponds to specific surface areas from about five to several hundred square meters per gram.

The filter element of cigarettes of the present invention is prepared by passing cyanamide-cellulose acetate tow through an aqueous suspension of highly particulate activated carbon until it has adsorbed the desired amount of the particles. The suspension may consist of l%-10% by weight of activated carbon particles suspended in water, which may contain one or more anti-flocculants for the carbon. The concentration of carbon in the suspension should -be such that the suspension is free fluid.

Dry activated carbon generally exists in aggregated or fiocculated state, and it is necessary to reduce these aggregates at least to pigmentary dimensions before contacting the cyanamide-cellulose acetate tow therewith. This may 'be done by ball milling the carbon as an aqueous slurry until the desired degree of comminution has been attained.

Preferably passage of the tow through the suspension is continued until the adsorptive capacity of the tow for the carbon black is substantially satisfied, i.e., until substantially no further weight increase results from continued residence of the tow in the suspension. This avoids non-use of the adsorptive sites introduced by the cyanamide on the one hand and causes as much carbon as possible to be adsorbed on filaments of the tow on the other hand.

Cellulose acetate tow is made by extruding cellulose acetate solution into a coagulating bath through a spinerette head /2"-l" in diameter containing 5,(l00-l5,000 microscopic holes, and crimping and washing (and if desired drying) the resulting tow. The tow thus consists essentially of thousands of smooth, crimped filaments of cellulose acetate in substantially parallel, loose array.

The cationic cyanamide-cellulose acetate tow used in the present invention may be prepared by treating cellulose acetate tow with an aqueous alkaline solution of free cyanamide (H NCN) to form a cationic nitrogenated product, and then treating the tow with an acid. Details of such a method are shown in Elizer et al., US. Patent 3,251,698. The treatment of the tow with cyanamide is carried at least to the point where the cellulose acetate is rendered cationic, as shown by the mobility of the product in an electrophoresis cell. The nitrogen content of such tow is small and is generally less than 0.2% of the dry weight of the tow, as determined by the Kjeldahl method. Preferably the treatment is carried as far as possible without significantly altering the physical properties of the tow. The reaction may be carried to the point where the product has a nitrogen content of 0.5% by weight and even larger amounts of cyanamide can be reacted with the cyanamide so as to form a tow containing more than this amount of nitrogen. The structural formula of cyanamide-cellulose acetate has not been ascertained, and while theoretical considerations indicate that the product may be described chemically as a guanyl cellulose acetate, the presence of guanyl substituents has not been proved. In the specification and claims, therescribe cellulose acetate which has been rendered cationic by reaction with cyanamide. 7

If desired, the tow leaving the aqueous suspension of highly particulate carbon may be dried and used in the manufacture of filter cigarettes without further treatment. However, a significant amount of carbon may be mechanically entrained by the tow and this amount may be sufficient to blacken the lips of those smoking cigarettes which contain the filter. It is therefore preferred td remove this entrained carbon, and this may be done before the tow is dried by mechanically agitating the tow in plain water which, if desired, may contain a surface active agent to facilitate the removal. In either event brief agitation causes disengagement and removal of substantially all of such mechanically entrained carbon. The carbon which remains is strongly adsorbed and remains attached to the filter material substrate while the cigarette is being smoked. The tow of the present invention is an efiicient adsorbent of vapors which are adsorbed by activated carbon in unsupported state but has substantially no filtering action on the particles which constitutethe solid phase of cigarettesmoke.

The invention will be morevparticularly illustrated by the examples which follow: These examples constitute preferred embodiments of the invention and are not to be construed as limitations thereof.

Example 1 Cationic cyanamide-cellulose acetate tow is prepared as follows:

A treating bath is prepared by adding 11.25 liters of water containing 0.75 kg. of NaOH to 3 liters of 50% aqueous cyanamide solution. The pH of the solution is 11. Through this solution at room temperature is slowly and continuously passed 2,222 g. of white well-crimped cellulose acetate tow (Estron-Eastman Chemical Co., 50,000 total denier). The dwell time of the tow in the solution is 10 minutes. The tow is-passed through squeeze rolls to provide an aqueous content about equal to the dry weight of the tow (100% solution pick-up). The tow is placed in a circulating hot air oven at 200 F. for 13 minutes and is then dry. The tow is immediately submerged in 4 liters of water containing 0.4 kg. of 37% hydrochloric acid (pH 1.3) for 15 minutes, after which the tow is squeezed, washed in four changes of water, and dried at 190 F. in an electric clothes drier.

The resulting tow is white and fiufiy and only slightly crimped, and weighs 2122 g. Its nitrogen content (Kjeldahl) is 0.12% based on its dry weight.

The tow thus prepared is converted into a carboncontaining filter material as follows:

An aqueous suspension of pigmentary activated car ban is prepared by ball-milling for 18 hours a slurry of 200 g. of 50 +200 mesh activated coconut shell carbon made into paste with 540 g. of water. The particles in the product are all finer than 44,; about 50% by weight of the particles are 26 in diameter, and many are of much greater fineness. Y

Through 184 g. of the above slurry made up to 1 liter,

with water is slowlypassed 50 g. of the'dry cyanamidecellulose acetate tow prepared as described above (dwell time 15 seconds). The tow is squeezed to remove free liquid, washed several times in water, and air dried. The resulting tow is jet black audcontains 12% carbon by weight. It possesses little tendency to blacken the hands when rubbed thereon. The tow does not release carbon as a dust when slapped upon a surface.

Example 2 The coarse activated carbon granules are removed from the tip of a commercial filter-tip cigarette. The dry carbon-containing cyanamidecellulosc tow of Example 1 is compressed to a rope about A? in diameter by manual twisting. The rope is pushed into the /2" cavity left by the granules and is cut off flush with the end of the cigarette. When the cigarette is smoked, the filter element removes tars from the smoke.

A process for manufacturing the filter elements disclosed herein is claimed in my divisional application Ser. No. 595,339, filed on Nov. 18, 1966.

I claim:

1. A smoke filter cigarette wherein the filter element comprises cationic cyanamide-cellulose acetate tow having an adsorbed content of pigmentary activated carbon. 2. A cigarette according to claim 1 wherein at least by. weight of said carbon has a particle size less than 5 microns.

3. A cigarette according to claim 1 wherein said tow contains substantially no unadsorbed activated carbon.

References Cited by the Examiner UNITED STATES PATENTS 2,754,829 7/1956 Hess 131-208 2,881,770 4/1959 Touey 131-208 FOREIGN PATENTS 11,419 1902 Great Britain.

LUCIE H. LAUDENSLAGER, Brimary Examiner. 

1. A SMOKE FILTER CIGARETTE WHEREIN THE FILTER ELEMENT COMPRISES CATIONIC CYANAMIDE-CELLULOSE ACETATE TOW HAVING AN ADSORBED CONTENT OF PIGMENTARY ACTIVATED CARBON. 